The present invention relates to a novel resin useful for coatings. More particularly, it relates to a resin for coatings, i.e. useful as a medium for printing inks, paints or the like, which contains a modified polymer produced by adding an .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof to a liquid conjugated diolefinic polymer having at least 50% of cis-1,4 structure, wherein the carboxyl group or the carboxylic anhydride group of the resulting adduct is diesterified, and thereby the acid value of the modified polymer is made substantially not more than 10.
Generally, the printing inks useful as a coating composition comprises a pigment, a medium and an auxiliary, i.e. a regulator for giving the composition suitable workability, drying characteristics and usability.
The medium may be usually drying oils, natural resins, processing natural resins, synthetic resins, bituminous substances, waxes, celluloses, rubber derivatives, solvents and plasticizers. As the drying oils linseed oil is mainly used, but Chinese tung oil, perilla oil and soybean oil may also be used. The natural resins and the processing natural resins include rosins, hardened rosins, polymerized rosins, rosin esters, maleic resins and shellac. The synthetic resins include phenol resins, phenol resins modified with rosin, xylene resins, modifed alkyd resins, polyamide resins, and coumaronindene resins. There may be used other mediums, such as chlorinated rubber, cyclized rubber, nitrocellulose and various solvents.
The auxiliary agent includes a drier for promoting the drying of the composition (e.g. lead naphthenate, cobalt naphthenate), or a drying inhibitor, or a perfume, a ultraviolet absorber, or the like.
Besides, paints are used as a coating composition. The paints comprise a pigment (as a colorant); a medium, such as drying oils (e.g. tung oil, linseed oil, or dehydrated castor oil), semi-drying oils (e.g. soybean oil, tall oil, or fish oil), natural resins (e.g. rosin, copal.multidot.dammar gum, or shellac) and synthetic resins (e.g. phenol resin, melamine resin, urea resin, coumaron resin, acrylic resin, polyester resin, polyvinyl chloride resin, or alkyd resin); an appropriate solvent and a metallic drier for promoting the drying of the composition.
However, the natural drying oils and the natural semi-drying oils used for coating compositions, such as printing inks or paints, are variable with the weather or the harvest, and therefore, it is very difficult to supply constantly a large amount of the products having good qualities.
Accordingly, it has been desired to develop a synthetic oil having the same or more excellent qualities and properties than those of the natural drying oil or the natural semi-drying oil.
Owing to the recent development in the petrochemistry, butadiene or other materials are easily available. Besides, the present inventors have found a process for producing an improved liquid polymer from diolefins, such as butadiene or isoprene, and it has now been found that a modified polymer having excellent properties and being usable for coating composition instead of the conventional natural drying oils or natural semi-drying oils can be produced from the liquid polymer.
An object of the present invention is to provide an improved resin suitable for coating composition, such as printing inks or paints.
Another object of the invention is to provide a modified polymer having an acid value of not more than 10, i.e. an adduct of a liquid conjugated diolefinic polymer having at least 50% of cis-1,4 structure with an .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof wherein the carboxyl group or the carboxylic anhydride group is diesterified.
A further object of the invention is to provide a printing ink containing the modified polymer as set forth above.
A still further object of the invention is to provide a paint containing the modified polymer as set forth above.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The resin for coatings of the present invention contains a modified polymer having not more than 10 of an acid value owing to the carboxyl group or the carboxylic anhydride group, which is produced by adding an .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof to a liquid conjugated diolefinic polymer having a number average molecular weight of 150 to 3,000, a viscosity of 2 to 5,000 cps at 30.degree. C. and not less than 50% of cis-1,4 structure and subjecting the resulting polymer adduct to diesterification.
The liquid polymer used in the present invention is characterized in that it has mainly cis-1,4 structure, which means that the present liquid polymer has an extremely lower viscosity in comparison with the conventional liquid polymer having predominantly vinyl structure. It is known that derivatives of a low molecular weight polybutadiene having predominantly vinyl structure are used for paints, but the derivatives have usually a high viscosity and therefore are limited in the use thereof. On the other hand, the liquid polymer having a wide range of molecular weight and having predominantly cis-1,4 structure of the present invention can be modified in the liquid state, and further, since it is liquid and has a low viscosity even after diesterified, it can give the desired ink or paint without using a diluent and can give a film having excellent toughness, plasticity and adhesion. Moreover, the liquid polybutadiene having predominantly cis-1,4 structure has a merit that in case of using as a printing ink it is easily cured when applied in a thickness of the film of 3 to 5.mu..
It is described in Japanese Patent Publication No. 11,195/1971 that a maleic anhydride adduct of a polybutadiene having predominantly vinyl structure, which is obtained by polymerizing butadiene in the presence of a catalyst system comprising an alkali metal, an organic compound of an alkali metal, an alkali metal-aromatic hydrocarbon complex, boron trifluoride etherate-water or a radical initiator, is semiesterified with an alcohol and then diesterified with an alkylene oxide to give an esterified compound containing a free hydroxy group in the molecule.
The maleic anhydride adduct of a polybutadiene has usually a higher viscosity with the increase of the addition amount of the maleic anhydride, which is, however, variable in accordance with the difference of the bonding manner of the butadiene unit in the polybutadiene. That is, the polybutadiene having vinyl structure shows extremely higher viscosity by the addition of maleic anhydride in comparison with the polybutadiene having cis structure. Accordingly, the polybutadiene having vinyl structure is remarkably restricted in the reactivity and in the utility thereof. For instance, the maleic anhydride adduct of a polybutadiene described in Japanese Patent Publication No. 11,195/1971 has a content of the combined maleic anhydride of about 8% (calculated from the acid value), a number average molecular weight of 970 and a viscosity of 20,000 cps at 25.degree. C.
On the other hand, the maleic anhydride adduct of the liquid polybutadiene having predominantly cis structure (the content of the combined maleic anhydride: 8% and the number average molecular weight: 1,080) in the present invention has a viscosity of only 620 cps at 25.degree. C., and when the adduct is diesterified according to the present invention, the viscosity thereof can be more reduced. For instance, as shown in Example 2 described hereinafter, the diesterified product derived from a liquid polybutadiene having predominantly cis-1,4 structure (the number average molecular weight: 1,000) shows a viscosity of 1,165 cps at 25.degree. C., while the content of the maleic anhydride thereof is 20%.
When a resin is used as a vehicle for printing inks, the presence of free hydroxy group in the resin gives undesirable effect on the printability. The product described in Japanese Patent Publication No. 11,195/1971 contains necessarily one hydroxy group per each maleic anhydride unit, but on the other hand, the product of the present invention does not contain any free hydroxy group.
The starting liquid conjugated diolefinic polymer used for the adduct in the present invention contains at least 50% of cis-1,4 structure and 0.5 to 10% of vinyl structure and the remaining percent of trans-1,4 structure (in case of polyisoprene, 3,4 structure being less than 30%) and has a number average molecular weight of 150 to 3,000 and a viscosity of 2 to 5,000 cps, preferably 2 to 2,000 cps at 30.degree. C.
Suitable examples of the liquid conjugated diolefinic polymer are a liquid polybutadiene, a liquid polyisoprene, a liquid copolymer of different kinds of conjugated diolefins, a liquid copolymer of a conjugated diolefin with a small amount of a monoolefin or an aromatic vinyl compound, or the like. In case of copolymer of butadiene or isoprene with styrene, the liquid copolymer contains not more than 40% by weight of styrene. These liquid conjugated diolefinic polymers can be produced by the methods described in Japanese Patent Laid Open Publication (without examination) Nos. 43,084/1973, 26,396/1974 and 89,788/1974, but any other method may be usable.
Other starting .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof used for the adduct in the present invention may be maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, or the like. Preferred one is maleic acid and maleic anhydride.
The adduct in the present invention can be produced by heating a mixture of at least one liquid conjugated diolefinic polymer and at least one .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof at an atmosphere of an inert gas at a temperature of 150.degree. to 250.degree. C. for 1 to 10 hours without using any catalyst. In this reaction, the .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof is quantitatively added to the liquid conjugated diolefinic polymer.
The adduct used in the present invention contains preferably 3 to 50% by weight, more preferably 10 to 40% by weight, of the .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof. When the content of the .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof is less than 3% by weight, the diesterified product derived from the adduct shows inferior properties, particularly insufficient compatibility with natural oils and fats or natural or synthetic resins and insufficient drying characteristics and film-forming properties, and on the other hand, when the content is over 50% by weight, the product derived therefrom has too high viscosity and can not practically be used.
The diesterification of the adduct of the liquid conjugated diolefinic polymer with the .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof can be carried out with alcohols having 1 to 27 carbon atoms. Suitable examples of the alcohols are saturated monovalent alcohols (e.g. methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, sec-amyl alcohol, diethylmethanol, isoamyl alcohol, tert-amyl alcohol, tert-butylmethanol, methylisopropylmethanol, n-hexyl alcohol, methylisobutylcarbinol, methylamylcarbinol, n-heptyl alcohol, methyl-n-amylcarbinol, n-octyl alcohol, capryl alcohol, 2-ethyl-n-hexyl alcohol, isooctyl alcohol, n-nonyl alcohol, n-decyl alcohol, n-undecyl alcohol, n-dodecyl alcohol, n-tridecyl alcohol, n-tetradecyl alcohol, n-pentadecyl alcohol, cetyl alcohol, stearyl alcohol, n-nonadecyl alcohol, behenyl alcohol, or cyclohexanol), unsaturated monvalent alcohols (e.g. allyl alcohol, propargyl alcohol, crotyl alcohol, oleyl alcohol, eraidyl alcohol, linoleyl alcohol, or geraniol), aromatic alcohols (e.g. benzyl alcohol, .beta.-phenylethyl alcohol, or hydrocinnamyl alcohol), ether alcohols (e.g. ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, furfuryl alcohol, or tetrahydrofurfuryl alcohol), or the like, which may be used alone or in a mixture of two or more kinds thereof. Among these alcohols, preferred one is the alcohol having 2 to 18 carbon atoms. Besides, divalent alcohols (e.g. ethylene glycol, diethylene glycol, propylene glycol, propanediol, or butanediol) may be used unless the product shows so high viscosity that the product is hardly used.
The diesterification reaction of the adduct with alcohols can be carried out in the conventional manner, for instance, by reacting the adduct with a somewhat excess amount, preferably 20 to 50 molar percent excess amount, of the alcohol at a temperature of 50.degree. to 250.degree. C., preferably 100.degree. to 200.degree. C., for 30 minutes to 8 hours in the presence of a catalyst such as inorganic acid (e.g. sulfuric acid, or hydrochloric acid) or an organic acid (e.g. para-toluenesulfonic acid), while the by-produced water is taken out from the reaction system. An appropriate solvent may be used in the reaction.
According to the above diesterification of the carboxyl group or the carboxylic anhydride group in the adduct, the modified polymer shows not more than 10 of an acid value owing to the carboxyl group or the carboxylic anhydride group. When the acid value of the polymer is over 10, the product shows undesirably inferior water resistance.
It is very important for obtaining the desired coating composition having excellent properties that the resin satisfies the above-mentioned conditions. That is, there are known some liquid conjugated diolefinic polymers, but they are not suitable for the coating composition of the present object because of the inferior dispersibility with pigments and the inferior compatibility with other various resins, natural drying oils or semi-drying oils. When the conventional liquid conjugated diolefinic polymers are used for the coating composition in the form of an adduct thereof with an .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof, the dispersibility with pigments and the compatibility with other resins are improved, but on the contrary, the acid value thereof becomes more than 30, and as the result, the stability thereof with pigments is remarkably reduced to induce the phrase separation, and further, owing to the rapid increase of the viscosity thereof, they are hardly used as the medium for printing inks or paints. Besides, in order to decrease the viscosity, the adduct of the conventional liquid conjugated diolefinic polymer with an .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof may be reacted with an alcohol to give a semi-esterified product, but the product is still not practically usable for coating compositions because it has still inferior stability with pigments owing to the high acid value thereof and further shows inferior water resistance.
The resin for coating of the present invention comprising the modified polymer, i.e. the adduct of the liquid conjugated diolefinic polymer with the .alpha.,.beta.-unsaturated dicarboxylic acid or anhydride thereof wherein the carboxyl group or the carboxylic anhydride group is diesterified is useful as a medium for printing inks and paints. When the resin of the present invention is used as one component of the printing inks or paints, it shows an excellent compatibility with the other various resinous components contained therein, and the resulting printing inks and paints show excellent characteristics. For instance, it is used for a printing ink for offset printing, the product shows an excellent adhesion onto the paper, particularly excellent drying characteristics, and therefore there can be obtained a good print having an excellent gloss. Moreover, the printing ink containing the resin of the present invention is remarkably excellent in the elimination of the dirts which occur in case of losing the balance between the dampening solution and the addition amount of the printing ink during the printing in comparison with the conventional printing ink containing the drying oil. Besides, the paint containing the resin of the present invention can give a glossy coating layer having excellent properties.
The printing ink of the present invention contains 3 to 50% by weight of the present resin and further an appropriate amount of the other components used in the conventional printing inks as mentioned hereinbefore, such as pigments, solvents, resins (e.g. natural resins, phenol resins, or xylene resins), driers, ultraviolet absorbents, or the like.
The paint of the present invention contains 5 to 80% by weight of the present resin and further an appropriate amount of the other components used in the conventional paints as mentioned hereinbefore, such as pigments, and optionally solvents, resins (e.g. phenol resins, alkyd resins), metallic driers, or the like.